I have a project that uses a small peristaltic pump to move water through a series of valves, the idea being that only one valve will be open at a time to control the water flow through my system. The amount of water I'm dealing with is relatively small (approx 50ml per hour).
My original project used an Arduino Uno, a small relay to control the pump, and several liquid solenoids to control the water movement through the system. The project worked great for a bench test, but for actual deployments I'd like to power this project using batteries for extended periods of time. And in order to meet my deployment time frame I need to bring my power consumption waaaay down.
I've replaced my Uno with a Arduino Pro Mini, and I replaced the relay that was controlling the pump with a MOSFET. Both of which brought my power consumption down. But the liquid solenoids (http://www.trossenrobotics.com/solenoid_valve) are proving to be quite power hungry, and I can't seem to find a good replacement for them.
Can anyone recommend a low power alternative to a liquid solenoid? If not a commercially available product, then some sort of system that will allow me to control the movement of water through a series of valves?
For 50ml per hour you can get much smaller solenoids. Parker have a number of different ranges of micro solenoids for different roles. I know of one application that runs a solenoid for months on two AA batteries.
How often do the solenoids need to switch? Do you hold one solenoid open for 10 minutes or is it very short squirts? You may be able to switch to a valve that stays in the last position it was set. Then you only drive the solenoids for a few milliseconds when changing the valve position.
Working on the basis of perilastic design, you could use a small servo type motor to squeeze the tube flat to stop the flow then de-power at that location. When you want flow, re-power servo and drive it to "un-squeeze" the tube then de-power again.
Perhaps a worm gear on the pump to prevent back-driving when the motor is powered off?
You want bistable solenoids, which use a pulse of one polarity to turn on, and the opposite
polarity to turn off, and which stay put when un-powered - such relays exist, not sure if
small liquid valves are available that do this.
Basically arrange that no power at all is needed except when the system is changing - they you
can sleep all the electronics down to micro-amp consumption levels, which is what will give you
long battery life.
jackrae:
Working on the basis of perilastic design, you could use a small servo type motor to squeeze the tube flat to stop the flow then de-power at that location. When you want flow, re-power servo and drive it to "un-squeeze" the tube then de-power again.